Service Bulletin CAB-33-07 recommends owners of Cessna 208B Caravans that fall within the listed serial numbers remove the ground shield on the wiring for LED/nav anti-collision lights. 

Field reports indicated that magnetometers were experiencing a red-x caused by interference from the lights. Removing the ground shield was found to eliminate the interference. 

Compliance with this bulletin is recommended to be completed at a future inspection or maintenance period.  

Read the service bulletin here.